Earth Notes

2:11 am

Wed January 23, 2008

Earth Notes - Forests and CO2

People have long looked to forests as our allies in the effort against climate change. Trees and other plants live by absorbing carbon dioxide, the greenhouse gas that's produced by the burning of fossil fuels. If more trees grow in more forests, then, they absorb more carbon, right?

They do but only up to a point. That's because most forests burn at some time. When they do, they release much of that trapped carbon back into the atmosphere.

A recent study by scientists from the University of Colorado and National Center for Atmospheric Research has estimated just how much carbon forest fires produce in North America. It sounds like a lot an average of over 300 million tons per year. But that's only about 5 percent of the amount people in North America send into the atmosphere by burning fossil fuels.

The study also showed that drought plays a role in how much carbon forests can store. During dry periods, like the one that's been gripping the Southwest in recent years, trees grow more slowly thereby absorbing less carbon dioxide from the air. They're also more likely to burn and give up all their carbon.

This means that trees in the Southwest probably can't help us out much especially if climate change makes the region warmer and drier, as many scientists predict. It won't be easy to control carbon dioxide that comes from tailpipes and smokestacks, but it's likely to be more effective than relying on plants to clean up after us.